The present invention relates to a temperature measurement device, particularly to a temperature measurement device for the cold junction of a non-contact temperature measurement element provided for not only increasing the accuracy of the temperature measurement from the detected object significantly, but also remaining the sensitivity thereof.
Accordingly, general temperature measurement devices may be substantially divided into contact temperature measurement devices and non-contact temperature measurement devices, wherein the contact temperature measurement devices have being replaced by the non-contact temperature measurement devices gradually due to features including convenience, speediness, accuracy, safety, and human-oriented design of the latter. Thus, the non-contact temperature measurement devices have become mainstream design of the temperature measurement product and been widely used in the ear thermometer, intelligent electric appliance, hazard mitigation, security system, automatic equipment, or remote sensing product.
Referring to FIG. 1, there is shown a conventional non-contact temperature measurement, characterized in that a heat-conductive and electrical-conductive base 13 may have four electrical-conductive pins 19 secured on the bottom side thereof, wherein three of the pins 19 may form element pins 197 electrically isolated from the base 13 by an insulating pad layer 193, and another pin 199 may be connected to the base 13 directly to form a base pin 199 electrically connected with the base 13. Moreover, an infrared temperature-sensing element 15 is secured in place on the top surface of the base 13, and connected to the two of the element pins 197 via a first connecting line 151 and a second connecting line 153, respectively. Furthermore, a thermistor 17 is secured on the other side of the top surface of the base 13. The bottom side of the thermistor 17 may be electrically connected to the base pin 199 via the base 13, and the top side thereof may be electrically to a pin-top 195 of the element pin 197, protruding from the top surface of the base 13, via a third connecting line 171. Additionally, a cap 11 made from a metal material is used to cover and protect the infrared temperature measurement element 15 and the thermistor 17. An area of the cap 11, opposite to a heat-absorption region 155 (hot junction) of the infrared temperature-sensing element 15, is provided with a window filter 115, such that the heat radiation power originated from an external detected object may be directly confronted to and absorbed by the heat-absorption region 155. The area designed for the cold junction is a region of the temperature-sensing element 15 excluding the heat-absorption region 155. Subsequently, the measured heat radiation power is combined with the measured ambient temperature value Ta (provided as the reference temperature value for the cold junction of the infrared temperature-sensing element 15), measured by the thermistor 17, and then the combined result will be transformed into the actual temperature Tb of the detected object.
Referring to FIG. 2, the object of the speediness, convenience, and the safety may be truly achieved by the conventional temperature measurement device. As the ambient temperature changes abruptly, the dynamic temperature-time curve 177 for the thermistor 17 is steeper in comparison with the dynamic temperature-time curve 157 for the infrared temperature-sensing element 15. In other words, the balance time t1 of the thermistor, provided for the reference temperature value for the cold junction of the infrared temperature-sensing element 15, is shorter than the balance time t2 of the actual cold junction of the infrared temperature-sensing element 15 itself, since the volume and the heat capacity of the infrared temperature-sensing element 15 are much larger than those of the thermistor 17. The inevitable difference in heat-balance time not only causes the queried accuracy with respect to the temperature measurement of the detected object, but also reduces the measurement sensitivity significantly.
For this reason, with a large amount of the effort and expense being invested by the industrial, there are attempts to diminish the difference between the heat-balance temperature curves of the thermistor and the cold junction of the infrared temperature-sensing element. The general development aspects are reducing the volume of the infrared temperature-sensing element or increasing the volume of the thermistor. However, if the improvement for reducing the volume of the infrared temperature-sensing element is desired, the signal of the temperature measurement may be deteriorated significantly, resulting in the significant reduction in the measurement sensitivity. On the contrary, if the improvement for increasing the volume of the thermistor is desired, the material of the thermistor and the expenditure thereof both need to be increased considerably.
Thus, providing a novel and efficient improvement construction with the increasing measurement accuracy and sensitivity for obviating disadvantages of the conventional temperature measurement device is critical to the present invention.
Accordingly, it is a primary object of the present invention to provide a temperature-sensing device diminishing effectively the difference between the temperature-balance curves for the cold junction of the infrared temperature-sensing element and the thermistor for increasing the temperature measurement accuracy of the detected object as the ambient temperature changes.
It is a secondary object of the present invention to provide a temperature measurement device diminishing effectively the difference between the heat capacities of the infrared temperature-sensing element and the thermistor without decreasing the volume of the infrared temperature-sensing element or increasing the volume of the thermistor for remaining the temperature measurement sensitivity.
It is another object of the present invention to provide a temperature measurement device increasing effectively the temperature measurement accuracy and sensitivity of the detected object with the minimum increase in manufacturing cost.
The structural features and the effects to be achieved may further be understood and appreciated by reference to the following description of the presently preferred embodiments together with the accompanying drawings, in which: